I'll offer part of it with comments from memory and some from my data base...
The "types" pretty much agreed on by those who sought the answers are below, T-1 to T-5. The T-6 thru T-9 types are still speculative, so I won't include them. Sights are another area of variations yet to be completely untangled as well for all barrel types... short, long, styles and heights. I do have a lot of it in my data base, but it is not complete. While some generalizations can be made, variations did exist within barrel types. But keep in mind that lots of variations have cropped up, factory run, "lunch time" oddities and such, all those modified by owners over the decades and those specifically made for TCA members only over the years with non standard lengths and for non standard cartridges that further cloud the mix. I doubt they will ever ALL be untangled now as few bother to work on doing so anymore with the Contender long discontinued, and the few at TC who could add info long retired or dead. I stopped trying long ago, never even started on the G2's, and while I did start a data base for the Encores their first years I dropped them as well after I sold all of mine.
Probably the only person left who could possibly confirm the remaining most likely "types" correctly for all of them if he cared and had the time is Ed K. I wouldn't hold you breath, he's a very busy man.
As for the barrel recoil blocks and bolts, in general the T-1 to T-4 vintage barrels "typically" need to be updated to the split bolts on Contenders made from the easy open vintage on - 1981 (from serial 195,000 on blue, all stainless and armor alloy "Contender" frames). I'll say typically only though because there have been some variations that worked fine without modifications, but I'm not going to try to remember and list them as most likely I'll forget some.
The barrel types I will offer, originally assembled by Ron Sable, but that I edited them with additions for inclusion in my data base AND never bothered to complete with additional data learned later.
T-1 Octagon: One line address, flat base barrel block, set screw for barrel bolt, short sight. 6 caliber's. T/C Arms Rochester N.H. followed by the caliber (there are variations also, including both 8 3/4" and 10" versions. Circa 1967
Pre Type 2 Octagon 10". Significant difference is the caliber is located at the muzzle end of the address.
T-2 Octagon 10": Has a two line address, flat base barrel block, set screw for barrel bolt. Significant identification is a period after the N.H. This type had the largest caliber selection. Circa 1967-1972.
T-3 Octagon 10": Also has a two line address, but now the period is only after the H. (not after the N). Flat base barrel block, set screw for barrel bolt, Circa 1973-1975. Bull barrels also found in this vintage.
T-4 Octagon 10": Two line address, flat base barrel block, barrel bolt set screw was changed to a roll pin to hold in bolt. There are both 10" bull barrels and 14" barrels in this vintage.
T-5 Octagon or bull: The significant change was from the flat base barrel block to a stepped one.
All I'll add, can't remember anymore nor care to debate it. Somebody else can carry on from here.
L.
